linux-kernel - Re: [PATCH v2] dt-bindings: hwmon: tda38640: Add interrupt & regulator properties

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Message-ID: <9cc60b90-329b-4065-a3c8-74c208964d45@roeck-us.net>
Date: Sat, 17 Feb 2024 07:57:43 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Conor Dooley <conor@...nel.org>
Cc: Naresh Solanki <naresh.solanki@...ements.com>,
 Jean Delvare <jdelvare@...e.com>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, mazziesaccount@...il.com,
 linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] dt-bindings: hwmon: tda38640: Add interrupt &
 regulator properties

On 2/15/24 03:48, Conor Dooley wrote:
> On Wed, Feb 14, 2024 at 05:17:04PM -0800, Guenter Roeck wrote:
>> On 2/14/24 11:55, Conor Dooley wrote:
>> [ ... ]
>>>>> Why "vout0" if there's only one output? Is it called that in the
>>>>> documentation? I had a quick check but only saw it called "vout".
>>>>> Are there other related devices that would have multiple regulators
>>>>> that might end up sharing the binding?
>>>>>
>>>>
>>>> Primarily because that is what the PMBus core generates for the driver
>>>> because no one including me was aware that this is unacceptable
>>>> for single-output drivers.
>>>
>>> Is it unacceptable? If you're implying that I am saying it is, that's
>>> not what I was doing here - I'm just wondering why it was chosen.
>>> Numbering when there's only one seems odd, so I was just looking for the
>>> rationale.
>>>
>>
>> Given the tendency of corporate speak (aka "this was a good attempt" for
>> a complete screwup), and since this did come up before, I did interpret
>> it along that line. My apologies if that was not the idea.
> 
> I'm not gonna go and decree that "vout0" is unacceptable, if it was
> called that in documentation that I had missed or was convention, I was
> just gonna say "okay, that sounds reasonable to me".
> 

"convention" only if lack of awareness how regulators are supposed to be named
is a convention.

>> Still, I really don't know how to resolve this for existing PMBus drivers
>> which do register "vout0" even if there is only a single output regulator.
> 
> I had a quick look at that series, none of the devices that I checked
> out there seem to have documented regulators at all. Some of the devices
> were only documented in trivial-devices.yaml. Relying on the naming of
> undocumented child nodes is a bug in those drivers & I guess nobody cares
> about dtbs_check complaints for those platforms. The example that was
> linked in the other thread doesn't even use a valid compatible :(
> 	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/aspeed/aspeed-bmc-delta-ahe50dc.dts?id=8d3dea210042f54b952b481838c1e7dfc4ec751d#n21
> I guess it uses the i2c device ids to probe on that platform, or have
> I missed something there?
> 

I think that is correct. If I recall correctly, the I2C subsystem no longer
searches for compatible drivers by only looking at the device id in the
compatible node, so I guess one has to list "lm25066" instead of "ti,lm25066"
as compatible to get a match in the i2c subsystem. That is of course
completely wrong.

Guenter